<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="../js/react.development.js"></script>
    <script src="../js/react-dom.development.js"></script>
    <script src="../js/babel.min.js"></script>
    <script src="../js/prop-types.js"></script>
</head>

<body>
    <div id="root"></div>
    <script type="text/babel">
        function LogIn() {
            return <h1>Welcome!</h1>;
        }
        function LogOut() {
            return <h1>Please log in.</h1>;
        }
        class Welcome extends React.Component {
            constructor(props) {
                super(props);
                this.state = {
                    isLogging: false,
                }
            }
            changeState = (prevState) => {
                this.setState((prevState) => ({
                    isLogging: !prevState.isLogging,
                }))
            }
            render() {
                const isLogging = this.state.isLogging;
                let greeting = null;
                if (isLogging) {
                    greeting = <LogIn />;
                } else {
                    greeting = <LogOut />
                }
                return (
                    <div>
                        {greeting}
                        <button onClick={this.changeState}>change state</button>
                    </div>
                )
            }
        }

        ReactDOM.render(<Welcome/>, document.getElementById('root'))
    </script>
</body>

</html>